Starkschall George, Forster Kenneth M, Kitamura Kei, Cardenas Alex, Tucker Susan L, Stevens Craig W
Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA.
Int J Radiat Oncol Biol Phys. 2004 Nov 15;60(4):1291-7. doi: 10.1016/j.ijrobp.2004.07.707.
To test the hypothesis that the magnitude of thoracic tumor motion can be used to determine the desirability of respiratory gating.
Twenty patients to be treated for lung tumors had computed tomography image data sets acquired under assisted breath hold at normal inspiration (100% tidal volume), at full expiration (0% tidal volume), and under free breathing. A radiation oncologist outlined gross tumor volumes (GTVs) on the breath-hold computed tomographic images. These data sets were registered to the free-breathing image data set. Two sets of treatment plans were generated: one based on an internal target volume explicitly formed from assessment of the excursion of the clinical target volume (CTV) through the respiratory cycle, representing an ungated treatment, and the other based on the 0% tidal volume CTV, representing a gated treatment with little margin for residual motion. Dose-volume statistics were correlated to the magnitude of the motion of the center of the GTV during respiration.
Patients whose GTVs were >100 cm(3) showed little decrease in lung dose under gating. The other patients showed a correlation between the excursion of the center of the GTV and a reduction in potential lung toxicity. As residual motion increased, the benefits of respiratory gating increased.
Gating seems to be advantageous for patients whose GTVs are <100 cm(3) and for whom the center of the GTV exhibits significant motion, provided residual motion under gating is kept small.
验证胸廓肿瘤运动幅度可用于确定呼吸门控是否可取这一假设。
20例拟接受肺癌治疗的患者在正常吸气（潮气量100%）、完全呼气（潮气量0%）及自由呼吸状态下获取了计算机断层扫描图像数据集。一名放射肿瘤学家在屏气计算机断层扫描图像上勾勒出大体肿瘤体积（GTV）。将这些数据集与自由呼吸图像数据集进行配准。生成了两组治疗计划：一组基于通过评估临床靶体积（CTV）在呼吸周期中的移动明确形成的内部靶体积，代表非门控治疗；另一组基于潮气量0%时的CTV，代表门控治疗且剩余运动余量较小。剂量体积统计数据与呼吸过程中GTV中心的运动幅度相关。
GTV大于100 cm³的患者在门控下肺剂量降低不明显。其他患者GTV中心的移动与潜在肺毒性降低之间存在相关性。随着剩余运动增加，呼吸门控的益处增加。
对于GTV小于100 cm³且GTV中心有显著运动的患者，若门控下的剩余运动保持较小，门控似乎是有利的。
